x86/entry: Convert NMI to IDTENTRY_NMI

Convert #NMI to IDTENTRY_NMI:
  - Implement the C entry point with DEFINE_IDTENTRY_NMI
  - Fixup the XEN/PV code
  - Remove the old prototypes

No functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135314.609932306@linutronix.de

arch/x86/entry/entry_32.S

@@ -1545,7 +1545,7 @@ SYM_CODE_END(double_fault)
  * switched stacks.  We handle both conditions by simply checking whether we
  * interrupted kernel code running on the SYSENTER stack.
  */
-SYM_CODE_START(nmi)
+SYM_CODE_START(asm_exc_nmi)
 	ASM_CLAC
 
 #ifdef CONFIG_X86_ESPFIX32
@@ -1574,7 +1574,7 @@ SYM_CODE_START(nmi)
 	jb	.Lnmi_from_sysenter_stack
 
 	/* Not on SYSENTER stack. */
-	call	do_nmi
+	call	exc_nmi
 	jmp	.Lnmi_return
 
 .Lnmi_from_sysenter_stack:
@@ -1584,7 +1584,7 @@ SYM_CODE_START(nmi)
 	 */
 	movl	%esp, %ebx
 	movl	PER_CPU_VAR(cpu_current_top_of_stack), %esp
-	call	do_nmi
+	call	exc_nmi
 	movl	%ebx, %esp
 
 .Lnmi_return:
@@ -1638,7 +1638,7 @@ SYM_CODE_START(nmi)
 	lss	(1+5+6)*4(%esp), %esp			# back to espfix stack
 	jmp	.Lirq_return
 #endif
-SYM_CODE_END(nmi)
+SYM_CODE_END(asm_exc_nmi)
 
 .pushsection .text, "ax"
 SYM_CODE_START(rewind_stack_do_exit)

arch/x86/entry/entry_64.S

@@ -1079,7 +1079,6 @@ idtentry_df	X86_TRAP_DF		double_fault		do_double_fault
 
 #ifdef CONFIG_XEN_PV
 idtentry	512 /* dummy */		hypervisor_callback	xen_do_hypervisor_callback	has_error_code=0
-idtentry	X86_TRAP_NMI		xennmi			do_nmi				has_error_code=0
 idtentry	X86_TRAP_DB		xendebug		do_debug			has_error_code=0
 #endif
 
@@ -1414,7 +1413,7 @@ SYM_CODE_END(error_return)
  *	%r14: Used to save/restore the CR3 of the interrupted context
  *	      when PAGE_TABLE_ISOLATION is in use.  Do not clobber.
  */
-SYM_CODE_START(nmi)
+SYM_CODE_START(asm_exc_nmi)
 	UNWIND_HINT_IRET_REGS
 
 	/*
@@ -1499,7 +1498,7 @@ SYM_CODE_START(nmi)
 
 	movq	%rsp, %rdi
 	movq	$-1, %rsi
-	call	do_nmi
+	call	exc_nmi
 
 	/*
 	 * Return back to user mode.  We must *not* do the normal exit
@@ -1556,7 +1555,7 @@ SYM_CODE_START(nmi)
 	 * end_repeat_nmi, then we are a nested NMI.  We must not
 	 * modify the "iret" frame because it's being written by
 	 * the outer NMI.  That's okay; the outer NMI handler is
-	 * about to about to call do_nmi anyway, so we can just
+	 * about to about to call exc_nmi() anyway, so we can just
 	 * resume the outer NMI.
 	 */
 
@@ -1675,7 +1674,7 @@ repeat_nmi:
 	 * RSP is pointing to "outermost RIP".  gsbase is unknown, but, if
 	 * we're repeating an NMI, gsbase has the same value that it had on
 	 * the first iteration.  paranoid_entry will load the kernel
-	 * gsbase if needed before we call do_nmi.  "NMI executing"
+	 * gsbase if needed before we call exc_nmi().  "NMI executing"
 	 * is zero.
 	 */
 	movq	$1, 10*8(%rsp)		/* Set "NMI executing". */
@@ -1709,10 +1708,10 @@ end_repeat_nmi:
 	call	paranoid_entry
 	UNWIND_HINT_REGS
 
-	/* paranoidentry do_nmi, 0; without TRACE_IRQS_OFF */
+	/* paranoidentry exc_nmi(), 0; without TRACE_IRQS_OFF */
 	movq	%rsp, %rdi
 	movq	$-1, %rsi
-	call	do_nmi
+	call	exc_nmi
 
 	/* Always restore stashed CR3 value (see paranoid_entry) */
 	RESTORE_CR3 scratch_reg=%r15 save_reg=%r14
@@ -1749,7 +1748,7 @@ nmi_restore:
 	 * about espfix64 on the way back to kernel mode.
 	 */
 	iretq
-SYM_CODE_END(nmi)
+SYM_CODE_END(asm_exc_nmi)
 
 #ifndef CONFIG_IA32_EMULATION
 /*

arch/x86/include/asm/idtentry.h

@@ -258,4 +258,8 @@ DECLARE_IDTENTRY_RAW(X86_TRAP_BP,	exc_int3);
 DECLARE_IDTENTRY_MCE(X86_TRAP_MC,	exc_machine_check);
 #endif
 
+/* NMI */
+DECLARE_IDTENTRY_NMI(X86_TRAP_NMI,	exc_nmi);
+DECLARE_IDTENTRY_XEN(X86_TRAP_NMI,	nmi);
+
 #endif

arch/x86/include/asm/traps.h

@@ -12,7 +12,6 @@
 #define dotraplinkage __visible
 
 asmlinkage void debug(void);
-asmlinkage void nmi(void);
 #ifdef CONFIG_X86_64
 asmlinkage void double_fault(void);
 #endif
@@ -20,14 +19,12 @@ asmlinkage void page_fault(void);
 asmlinkage void async_page_fault(void);
 
 #if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)
-asmlinkage void xen_xennmi(void);
 asmlinkage void xen_xendebug(void);
 asmlinkage void xen_double_fault(void);
 asmlinkage void xen_page_fault(void);
 #endif
 
 dotraplinkage void do_debug(struct pt_regs *regs, long error_code);
-dotraplinkage void do_nmi(struct pt_regs *regs, long error_code);
 dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsigned long cr2);
 dotraplinkage void do_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address);
 

arch/x86/kernel/idt.c

@@ -74,7 +74,7 @@ static const __initconst struct idt_data early_idts[] = {
  */
 static const __initconst struct idt_data def_idts[] = {
 	INTG(X86_TRAP_DE,		asm_exc_divide_error),
-	INTG(X86_TRAP_NMI,		nmi),
+	INTG(X86_TRAP_NMI,		asm_exc_nmi),
 	INTG(X86_TRAP_BR,		asm_exc_bounds),
 	INTG(X86_TRAP_UD,		asm_exc_invalid_op),
 	INTG(X86_TRAP_NM,		asm_exc_device_not_available),
@@ -186,7 +186,7 @@ gate_desc debug_idt_table[IDT_ENTRIES] __page_aligned_bss;
  */
 static const __initconst struct idt_data ist_idts[] = {
 	ISTG(X86_TRAP_DB,	debug,			IST_INDEX_DB),
-	ISTG(X86_TRAP_NMI,	nmi,			IST_INDEX_NMI),
+	ISTG(X86_TRAP_NMI,	asm_exc_nmi,		IST_INDEX_NMI),
 	ISTG(X86_TRAP_DF,	double_fault,		IST_INDEX_DF),
 #ifdef CONFIG_X86_MCE
 	ISTG(X86_TRAP_MC,	asm_exc_machine_check,	IST_INDEX_MCE),

arch/x86/kernel/nmi.c

@@ -503,8 +503,7 @@ static bool notrace is_debug_stack(unsigned long addr)
 NOKPROBE_SYMBOL(is_debug_stack);
 #endif
 
-dotraplinkage notrace void
-do_nmi(struct pt_regs *regs, long error_code)
+DEFINE_IDTENTRY_NMI(exc_nmi)
 {
 	if (IS_ENABLED(CONFIG_SMP) && cpu_is_offline(smp_processor_id()))
 		return;
@@ -554,7 +553,6 @@ do_nmi(struct pt_regs *regs, long error_code)
 	if (user_mode(regs))
 		mds_user_clear_cpu_buffers();
 }
-NOKPROBE_SYMBOL(do_nmi);
 
 void stop_nmi(void)
 {

arch/x86/xen/enlighten_pv.c

@@ -609,13 +609,18 @@ struct trap_array_entry {
 	.xen		= xen_asm_##func,		\
 	.ist_okay	= ist_ok }
 
+#define TRAP_ENTRY_REDIR(func, xenfunc, ist_ok) {	\
+	.orig		= asm_##func,			\
+	.xen		= xen_asm_##xenfunc,		\
+	.ist_okay	= ist_ok }
+
 static struct trap_array_entry trap_array[] = {
 	{ debug,                       xen_xendebug,                    true },
 	{ double_fault,                xen_double_fault,                true },
 #ifdef CONFIG_X86_MCE
 	TRAP_ENTRY(exc_machine_check,			true  ),
 #endif
-	{ nmi,                         xen_xennmi,                      true },
+	TRAP_ENTRY_REDIR(exc_nmi, exc_xennmi,		true  ),
 	TRAP_ENTRY(exc_int3,				false ),
 	TRAP_ENTRY(exc_overflow,			false ),
 #ifdef CONFIG_IA32_EMULATION

arch/x86/xen/xen-asm_64.S

@@ -32,7 +32,7 @@ xen_pv_trap asm_exc_divide_error
 xen_pv_trap debug
 xen_pv_trap xendebug
 xen_pv_trap asm_exc_int3
-xen_pv_trap xennmi
+xen_pv_trap asm_exc_xennmi
 xen_pv_trap asm_exc_overflow
 xen_pv_trap asm_exc_bounds
 xen_pv_trap asm_exc_invalid_op